As you approach retirement age, most experts agree you should gradually shift more into bonds to protect the money you've accumulated. But retirement can last a few decades, so it generally pays to maintain a healthy dose of stocks well into retirement: possibly between 40% and 50% while you're in your 70s, and up to 30% when you're in your 80s.

If you want to put your asset allocation on autopilot, consider "target-date retirement funds," which are available in many retirement plans. You simply choose a fund that's labeled with the year you intend to retire, and it will automatically adjust what it invests in (usually a mix of stocks, bonds and cash) to maximize your return and minimize your risk as you get older.